In this chapter, Zinn focuses on the idea that both state and federal government always took the side of the rich employers and land owners over the workers and renters. He does not talk much about monopolies per se. Instead, he is talking more generally about pro-business actions.

What Zinn says is that the governments helped businesses keep control of workers (and to some extent helped them have monopolistic powers) through laws that were passed in response to bribes. He says, for example, that

State legislatures gave charters to corporations giving them legal rights to conduct business, raise money...

He talks about how firms were willing to bribe legislators to get favorable legislation and he talks about how this led to them having excessive market shares. For example, he says

By 1850, fifteen Boston families called the "Associates" controlled 20 percent of the cotton spindleage in the United States, 39 percent of insurance capital in Massachusetts, 40 percent of banking resources in Boston.

However, he does not really specify what actions by the governments are supposed to have made this possible.

Overall, Zinn is trying to make the point that class conflict was important in antebellum America. As part of this, he does mention monopolies to some extent, but that is not the focus of the chapter.